Now, 20-year-old Sinclair tells us ... the Playboy heir has physically abused her on SEVERAL OCCASIONS ... but she's still willing to forgive the guy.

"I don't condone domestic violence, but if one ounce of good can come from this bad experience, then I can live with it and move on" ... Claire says.

"That is why I will not press charges against Marston Hefner if he keeps his word to give a public apology for physically abusing me on several occasions, and seeks psychiatric help for his anger issues."

Hugh also released a comment on the situation ... saying, "If they care about each other, they'll patch it up."